修正删除文档不能同时删除图片的bug

backend/src/llm/siliconflow.py

@@ -178,14 +178,24 @@ class SiliconFlowLLM:
         import asyncio
         import time
 
-        # 读取图片并编码为base64
-        with open(image_path, "rb") as f:
-            image_data = base64.b64encode(f.read()).decode("utf-8")
-
-        # 检测图片格式
+        # 读取图片并编码为base64，不支持的格式先转为PNG
         ext = os.path.splitext(image_path)[1].lower()
         mime_map = {".png": "image/png", ".jpg": "image/jpeg", ".jpeg": "image/jpeg", ".gif": "image/gif", ".webp": "image/webp"}
-        mime_type = mime_map.get(ext, "image/png")
+
+        if ext not in mime_map:
+            from PIL import Image
+            import io
+            img = Image.open(image_path)
+            if img.mode in ("CMYK", "P"):
+                img = img.convert("RGB")
+            buf = io.BytesIO()
+            img.save(buf, format="PNG")
+            image_data = base64.b64encode(buf.getvalue()).decode("utf-8")
+            mime_type = "image/png"
+        else:
+            with open(image_path, "rb") as f:
+                image_data = base64.b64encode(f.read()).decode("utf-8")
+            mime_type = mime_map[ext]
 
         prompt = IMAGE_DESCRIPTION_PROMPT.format(context_text=context_text[:600])